What to do if insurance company not providing interest on delay

I booked a flat in virar Mumbai under the "life ka chance" offer in july 2016. In this life ka chance offer, ekta world through advertisements and initial sales process assured home buyers that they will be covered by a third-party insurance in case of delay of delivery (Fit-out) with a 9% P. A. Interest by the insurance company. I have already paid 82% of the flat cost 25.65 lacs. My wings fit-out date was august 2017. However there was no work done in my wing from july 2016 to august 2017. In august 2017 i was told that there is a 6 months grace period and by february 2018 if the wing is ready upto fit out then i will be eligible to get interest. In february 2018  i was told that builder has paid the premium but the insurance company which covered this interest for delay is closed. The offer advertisement is available.